The haptor is the attachment organ of the monogeneans, a group of parasitic Platyhelminthes. The haptor is sometimes called opisthaptor (from opistho-: behind) to emphasize that it is located in the posterior part of the body, and to differentiate it from the prohaptor (from pro-: in front), a structure including glands located at the anterior part of the body. According to Yamaguti (1963), [3] the chief adhesive organ of the monogeneans, the haptor, is posterior, more or less discoid, muscular, may be divided into alveoli or loculi, is usually provided with anchors, has nearly always marginal larval hooklets, or is in a reduced form with anchors. The haptor may consist of symmetrical or asymmetrical, sessile or pedunculate, muscular suckers or clamps with or without supporting sclerites; accessory adhesive organs may be present in form of armed plaques, lappets or appendices.
The structure of the haptor is different in the two major groups constituting the Monogenea, namely the Polyopisthocotylea and the Monopisthocotylea, and is an important part of the diagnosis in both groups.
Monogeneans are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they have both male and female reproductive structures.
Polyopisthocotylea is a subclass of parasitic flatworms in the class Monogenea.
The Monopisthocotylea are a subclass of parasitic flatworms in the class Monogenea.
Protomicrocotylidae is a family of monogenean parasites in the order Mazocraeidea.
Clamps are the main attachment structure of the Polyopisthocotylean monogeneans.
These ectoparasitic worms have a variable number of clamps on their haptor ; each clamp is attached to the host fish, generally to its gill. Clamps include sclerotised elements, called the sclerites, and muscles. The structure of clamps varies according to the groups within the Polyopisthocotylean monogeneans; microcotylids have relatively simple clamps, whereas gastrocotylids have more complex clamps.
Lethacotyle is a genus of polyopisthocotylean monogeneans, included in the family Protomicrocotylidae.
The genus includes only two species: Lethacotyle fijiensisManter & Price, 1953 , the type-species of the genus, and Lethacotyle veraJustine, Rahmouni, Gey, Schoelinck, & Hoberg, 2013 . Both species are parasitic on the gills of jacks in the Pacific Ocean. They are known only from three localities: off Fiji, Andaman Islands, and New Caledonia.
The genus Lethacotyle is special in that its members have no clamps on their posterior attachment organ or haptor, in contrast to most polyopisthocotylean Monogenean which have clamps. This is reflected in the etymology of the name, which, according to Manter & Price is "from letha = forgetting, and cotyle = cup, and refers to the absence of clamps".
Lethacotyle vera is a species of monogenean of the family Protomicrocotylidae.
The Capsalidae is a family of monopisthocotylean monogeneans, which includes about 200 species.
Calydiscoides is a genus of monopisthocotylean monogeneans, included in the family Diplectanidae.
Chimaericola leptogaster is a species of polyopisthocotylean monogenean in the family Chimaericolidae. It is ectoparasitic on the gills of the chimaera Chimaera monstrosa.
Microcotyle fusiformis is a species of monogenean, parasitic on the gills of a marine fish, described by Seitarō Gotō in 1894. It belongs to the family Microcotylidae. This species was first.
Microcotyle polymixiae is a species of monogenean, parasitic on the gills of a marine fish. It belongs to the family Microcotylidae. It was first described and illustrated based on 82 whole mounts, from the gills of the silver eye, Polymixia japonica (Polymixiidae) off Hawaii.
Pseudorhabdosynochus hargisi is species of a diplectanid monogenean parasitic on the gills of the White grouper Epinephelus aeneus. It was described in 1984 as Diplectanum hargisi and transferred to the genus Pseudorhabdosynochus by Santos, Buchmann & Gibson in 2000. Its systematic position has been clarified by Kritsky, Bakenhaster & Adams in 2015, who differentiated it from Pseudorhabdosynochus americanus.
Pseudorhabdosynochus riouxi is a species of diplectanid monogenean parasitic on the gills of dusky grouper Mycteroperca marginata. It was described by Guy Oliver in 1986 as Cycloplectanum riouxi, then transferred to the genus Pseudorhabdosynochus by Santos, Buchmann & Gibson in 2000. The species has been redescribed by Chaabane et al. in 2017.
Microcotyle sebastis is a species of monogenean, parasitic on the gills of a marine fish. It belongs to the family Microcotylidae.
Pseudaxine is a genus which belongs to the phylum Platyhelminthes and class Monogenea; all its species are parasites of fish.
Pseudaxine trachuri is a species of monogenean, parasitic on the gills of a marine fish. It belongs to the family Gastrocotylidae.
Pseudaxine indicana is a species of monogenean flatworm, which is parasitic on the gills of a marine fish. It belongs to the family Gastrocotylidae.
Sibitrema is a genus which belongs to the phylum Platyhelminthes and class Monogenea; the only species included in this genus is parasite of fish.
Sibitrema poonui is a species of monogenean flatworm, which is parasitic on the gills of a marine fish. It belongs to the family Gastrocotylidae.